1. Field of the Invention
The present invention relates to a double tapered filament for a power toothbrush and a method for manufacturing the same. More particularly, the present invention relates to a double tapered filament having excellent durability even with a short length so as to be suitable for the use in a power toothbrush, and a method for manufacturing the same.
2. Description of Related Art
A filament for a toothbrush, which is first made of nylon, has been significantly changed with development of various tapered filaments using polybutylene terephthalate (PBT). Current tapered filament is increasingly demanded by many people since the filament has solved the problems of existing filament made of nylon, such as bending and sanitation, and has excellent accessibility to a periodontal pocket. In addition, various toothbrushes having a functional filament or changed tufting form, which is beyond the established viewpoints, have been introduced, and new types of high-grade toothbrushes using electric power or ultrasonic wave have also been developed.
However, the filament used in a power toothbrush has two important features. First, the filament is required to maintain its stiffness or strength in a toothbrush rotating at high speed; and second, a part of a brush head connected with a power part has a predetermined thickness and thus a tufting length of a brush part except for the connection part should have a quite shorter length than that of a manual toothbrush (general toothbrush). That is, since a tuft part of the power toothbrush has a thickness greater than that of a manual toothbrush, the length of the filament of the power toothbrush should have a relatively short length in order to control an overall height of the toothbrush.
Particularly, unlike the general filament which is tufted into the brush head in a “V” shape and then cut to a predetermined length, in the case of the tapered filament, the tapered filament is previously manufactured so as to have two tapered ends and then tufted into the brush head. Therefore, to tuft this tapered filament into the power toothbrush, it is important for the tapered filament to maintain its short overall length as well as have a short taper with a uniform shape.